As Ohio’s attorney general during the fallout from the financial crisis, Mr. Cordray undertook a series of prominent lawsuits against big names in the finance world, including Bank of America. After narrowly losing re-election in late 2010, he came to Washington to lead the bureau’s enforcement efforts.

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“There’s a belief here that Wall Street is a fixed casino and it’s back in business, and we’re left holding the bag,” Mr. Cordray, then speaking from his office as Ohio’s attorney general, told The New York Times last year. “It’s important for us to show we’ll go after a company that does wrong.”

Mr. Obama, when introducing Mr. Cordray to the media at the White House on Monday, reinforced the nominee’s image as a reformer, praising his past efforts to tackle “unscrupulous lenders.”

Wall Street has been largely silent about Mr. Cordray’s appointment, with few financial trade groups willing to say anything much publicly about him.

The Consumer Bankers Association used the event to provide a broader attack of the bureau. “As we have stated repeatedly, we would prefer to see the bureau run by a commission” like other agencies, it said in a statement, “even the Consumer Product Safety Commission, which was the model for the creation of the C.F.P.B.”

Others treaded more lightly. “We look forward to a productive opportunity to engage with the new leadership of the C.F.P.B.,” said David H. Stevens, president and chief executive of the Mortgage Bankers Association.

Behind closed doors, some industry officials questioned whether life under Mr. Cordray would be easier than it would have been if Mr. Obama chose Elizabeth Warren to lead the bureau. Mr. Cordray was one of the first people recruited to the bureau by Ms. Warren, the Harvard professor and consumer advocate who has been setting up the fledgling agency.

As far as Wall Street is concerned, Ms. Warren and Mr. Cordray are philosophically aligned on most issues. While Ms. Warren conducted a lengthy charm campaign, meeting with bankers from every state to subdue some criticism, Mr. Cordray spent the last several months deciding which types of enforcement cases to pursue against the industry.

Here is a look at some cases that made Mr. Cordray, as Ohio’s attorney general, the Midwestern sheriff of Wall Street.

CREDIT RATING AGENCIES

While federal officials issued reports chiding the nation’s top credit rating agencies, Mr. Cordray took them to court. In 2009, he sued the firms, saying that they awarded top grades to troubled mortgage-backed securities and also were “intimately involved in structuring” the investments. The products, he said, caused retirement funds to lose hundreds of millions of dollars. The suit is still pending.

“The rating agencies’ total disregard for the life’s work of ordinary Ohioans caused the collapse of our housing and credit markets and is at the heart of what’s wrong with Wall Street today,” he said at the time.

GMAC

Last fall, Mr. Cordray became one of the first attorneys general to take action in the nationwide investigation of wrongful foreclosures. His target was GMAC Mortgage and its parent, Ally Financial. Mr. Cordray sued the firms, arguing that they had used bogus paperwork to foreclose on homes. He sought to collect up to $25,000 for each foreclosure.

“It’s now becoming clear that fraud, deception and an utter disregard for accuracy are in part to blame for the national foreclosure disaster,” he said at the time. The suit is pending.

In 2008, his office sued Merrill Lynch on behalf of the state’s teacher pension funds. Mr. Cordray said that Merrill had artificially inflated its stock price, which fell after the bank had losses on subprime mortgages. Merrill settled for $475 million.

He later led a multistate lawsuit against Bank of America over its takeover of Merrill. “The amount of shareholder value affected here, negatively, is about as great as has been alleged in any case, ever,” Mr. Cordray said at the time about the suit, which is also pending.